Field of the Invention
The present invention relates to a substrate cleaning apparatus and a substrate cleaning method for performing scrub cleaning of a surface of a substrate, such as a semiconductor wafer, with an elongated cylindrical roll cleaning member extending horizontally, by rotating the substrate and the roll cleaning member each in one direction while keeping the roll cleaning member in contact with the surface of the substrate.
Description of the Related Art
In a cleaning apparatus for performing scrub cleaning of a surface of a substrate, such as a semiconductor wafer, with a roll cleaning member, the roll cleaning member is rotated and pressed against the substrate under a predetermined pressing load (roll load) during cleaning of the substrate. Controlling and adjusting the roll load to an appropriate value is important to increase the cleanliness of the substrate or to prevent the substrate from being damaged.
Therefore, the applicant of the present invention has proposed a substrate cleaning apparatus having a closed-loop feedback control (CLC) system in which the pressing load (roll load) for pressing the roll cleaning member against the substrate is measured by a load cell during cleaning of the substrate to control a regulating device of an actuator, such as a motor, based on the measured values, thereby controlling the roll load to an appropriate value by feedback control, as disclosed in Japanese laid-open patent publication No. 2002-50602.
In the case where the pressing load (roll load) for pressing the roll cleaning member against the substrate is measured by the load cell to control the roll load based on the measured values by feedback control during cleaning of the substrate, if the roll load is not measured accurately due to breakdown of the load cell, an appropriate roll load cannot be applied to the substrate by the roll cleaning member.
Specifically, if the measured value (measured roll load) of the load cell becomes larger than the actual roll load due to breakdown of the load cell, a roll load which is smaller than the predetermined roll load is applied to the substrate by the roll cleaning member, thus reducing the cleaning ability for the substrate. On the other hand, if the measured value (measured roll load) of the load cell becomes smaller than the actual roll load, a roll load which is larger than the predetermined roll load is applied to the substrate by the roll cleaning member, thus possibly causing breakage of the substrate.